This invention relates generally to door closers and more particularly to a method for making door closers which are designed for economical manufacture by molding and for simple assembly by reduction of the number of parts and elimination of secondary machining operations.
FIG. 1 shows a door closer 10 of the prior art to be assembled from a large number of parts. A housing body 11 is threaded 22 to a spring housing 12. Endplug 14 and spring plug 13 are likewise threaded 21, 23 to housing body 11 and spring housing 12, respectively. Pinion 16 engages the rack (not shown) of piston 15 and is held in place in housing body 11 by two packing nuts 17 which provide support for the pinion shaft seals (not shown) and bearings 18.
Housing body 11 is drilled and cross drilled for fluid ports (not shown) through which fluid flow is controlled by needle valves (not shown) to regulate door closing and latching speeds. Other designs of door closers are in use, one such device being substantially as described in U.S. Pat. No. 4,386,446, granted Jun. 7, 1983 to Zunkel, et al and commonly assigned herewith. For details of construction and operation of door closers, the specification ('446) Patent is incorporated herein by reference.
Although this general design has been in use in various forms for a long time, and although it provides door closers of excellent strength and durability, it is costly and time consuming to perform the many machining, finishing, and assembly operations. These many operations also introduce a high probability for error with resultant scrap losses. For example, both ends of the housing body and the spring housing as well as the end plugs must be threaded in order to be assembled together. In addition, the transverse pinion bore must be threaded at both ends to receive the externally threaded packing nuts, and the bores of the nuts must also be finished to close tolerance to accommodate the bearings. The drilling, cross-drilling, and tapping of the fluid ports in the housing body and the drilling, ball seating, and staking of the check valves in the piston ends are also costly and time consuming precision machining operations required by the design. Clearly, the greater the degree of precision required by any machining, the greater is the risk of a discrepant result and attendant rework and scrap losses.
The foregoing illustrates limitations known to exist in present hydraulic door closers, and it would be advantageous to provide an alternative directed to overcoming one or more of those limitations. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.